Effect of slurry injection system position on removal rate for shallow trench isolation chemical mechanical planarization using a cerium dioxide slurry

In this study, the effects of ultrapure (UPW) water dilution of a ceria-based slurry on silicon dioxide removal rates were investigated. Results indicated that removal rates increased with dilution up to a slurry to UPW ratio of 1:7.5 before reaching a plateau in the pre-mix dilution case. The concentration of Ce³⁺ was thought to increase with dilution up to a ratio of 1:7.5. Further dilution resulted in reduced friction and temperature which halted any further increases in removal rate. Mixing the slurry and UPW at point-of-use resulted in a similar removal rate trend to pre-mixing, but with higher removal rates at each dilution ratio due to reduced particle agglomeration. A novel slurry injection system (SIS) was employed at various rotation angles. Each SIS angle produced a different retaining ring bow wave thickness, which led to different extents of dilution and therefore different removal rates. The SIS at-8° produced the highest removal rates of all angles at an average value of 2,595 Å/min. A third dilution ratio test was performed using point-of-use mixing through the SIS at-8°, which resulted in a similar removal rate trend as the previous tests but with dramatically higher removal rates at each dilution ratio.